Engine piston



May 19 1936. E. NELSON 4 ,5

ENGINE PISTON Filed Aug. 27, 1954 2 Sheets-Sheet l Ema/mm Emil-M31801,

19, 1936. Y E NELSON 2,041,567

' ENGINE PISTON Filed Aug. 27, 1954 2 Sheets-Sheet 2 Jim-11:1lvzez mp,

Patented May 19, 1936 STT S EAENT GFFIE Application August 27,

2 Claims.

This invention relates particularly to pistons of theinternal-combustion-engine type.

It is an object of the invention to provide improved means to compensatefor wear and to avoid piston slap. For this purpose, the inventionprovides rigid detachable auxiliary skirts for the piston that may beadjusted at right angles to the axis thereof. With skirts of the formand arrangement provided by the invention, use of piston-skirt expandersand pistonring expanders with their attendant disadvantages is avoided.

Heretofore, springs have been used to urge shoes or other piston-skirtparts, and in some instances packing-rings, against the cylinder-wall,but springs have been found initially to be not suf-, ficientlyresistive to thrust pressure and power stroke, they become weakenedduring use under the high temperatures to which subjected, and.oftentimes they break. A piston that includes spring elements is notsuitable for internal-combustion engines.

The skirt of a piston is a guide for its head, which carries the rings,and the rings should contact squarely against the cylinder-wall tofunction properly. A piston-skirt having elements urged laterally bysprings against the cylinderwall may not slap under thrust pressure, butit has such give as causes the rings to break their seal with thecylinder-wall, the rings wear round on their faces, and the ring-groovesbecome worn.

In order that rings and piston can function properly, the piston headand skirt together must be rigid, as loose skirts and those that includespring action result in impairment and eventual elimination of sealingof the rings with the cylinder-wall.

Some prior art forms of pistons are susceptible to bending in the medianportion of the skirt and liable to breakage at that place; and, whenbending occurs, the head rocks, ring seal is broken, the ring-faces wearround, and the ring-grooves also wear.

With some forms of pistons having laterallyurging springs, the pistonslap the springs are intended to obviate is accentuated in somecircumstances; and, if the springs are strong enough to withstand thrustpressure, they exert such outward pressure against the cylinder-wallthat lubricant film is wiped off with the result that there is too muchfriction, the resultant temperature breaks down lubricant, and pistondrag occurs that materially decreases the efficiency of the engine.

Therefore, in order to avoid diificulties and de- 1934, Serial No.741,672

fects such as the foregoing, the invention provides a skirted piston,diametrically adjustable in its skirt, that is as rigid as if cast as a.single piece.

When considered with the description herein, the characteristics of theinvention are apparent from the accompanying drawings, forming parthereof, wherein there is exemplified, for purposes of illustration, anembodiment of the invention now deemed to be a preferable one.

Like reference-characters refer to corresponding parts in the views ofthe drawings, of which- Fig. 1 is an elevational View of the piston;

Fig. 2 is an elevational View of another side of the piston;

Fig. 3 is a sectional view on the line 33, Fig. 2;

Fig. 4. is a bottom view of the piston;

Fig. 5 is a view of the piston in a lathe;

Fig. 6 is an elevational view of a shim;

Fig. 7 is a plan view of a shim;

Fig. 8 is a sectional view on the line 88, Fig.

Fig. 9 is an elevational view of a piston with removable skirts;

Fig. 10 is an elevational view of another side of the piston withremovable skirts;

Fig. 11 is a bottom view of a piston with removable skirts;

Fig. 12 is a bottom view of a removable skirt;

Fig. 13 is a top view of that skirt;

Fig. 14 is an elevational view thereof;

Fig. 15 is a sectional view on the line l5-l5, Fig. 14.

The upper portion of the piston, including its head I6, circumferentialgrooves I! containing packing-rings l8, and wrist-pin bearings or bossesI9, is of conventional form.

The piston-skirt 20, which is formed integrally and rigidly with thehead, is of less diameter than the head and the cylinder in which it isto work. At diametrically opposite places in a line at right angles tothe axis of the wrist-pin bosses, the skirt is flattened exteriorly fromtop to bottom, as shown at 21, but elsewhere its outer surface isarcuate and concentric with the piston axis.

The wall of the skirt is cut away at the bottom, as shown at 22 and 23,to enable it to take the chuck of a lathe, as shown by Fig. 5.

The skirt is formed with holes 24 to accommodate fastem'ngs, to whichreference hereinafter is made.

Two transversely arcuate rigid auxiliary skirts 25 are provided forremovable attachment to the integral piston-skirt proper. Each of themis formed with a thickened longitudinal portion 26 having a flattenedinside surface corresponding in area to, and arranged to seat against, aflattened part 2i of the integral skirt. The interior contour of theauxiliary skirt corresponds exactly to that of the outside surface ofthe integral skirt against which it is to abut. Each of the auxiliaryskirts has holes 21 and countersinks 23 in its portion 26 toaccommodate, respectively, the shanks 29 and heads 30 of bolts 3| bywhich it is secured to the integral skirt. The bolts extend through theparts, and they are held fast by nuts 32 on their inner ends. The nutsare tightened to draw and hold the auxiliary skirts rigidly against theintegral skirts. The countersinks are sufficiently deep to house thebolt-heads inside of the outer periphery, in order to avoid contact ofthe heads with, and scoring of, the cylinder-Wall.

The auxiliary skirts are of such thickness and exterior contour when newthat they have normal working contact with the cylinder-wall when theyare on the integral skirt.

When, during use, the auxiliary skirts become worn to the extent thatthey no longer function efficiently as guides that prevent thepiston-head from tilting, the piston from slapping, and the rings fromwearing round, one or more thin shims 33, such as shown by Figs. 6 and7, are placed inside of them, and the auxiliary skirts are replaced onand reattached to the integral skirt. Each of the shims is of a shapeand size to seat against a side of the integral skirt such as shown byFig. l, and it has holes 34 to accommodate the fastenings.

At first, after wear, the number of shims (one or more) required toextend the outer surfaces of the auxiliary skirts to normal workingcontact with the cylinder-wall are used. Subsequently, additional shimsmay be inserted from time to time, until the auxiliary skirts havebecome so worn that it is necessary to discard them, when new auxiliaryskirts may be brought into use.

When the removable auxiliary skirts are incorporated into the pistonstructure, either without or with shims, they are rigid andsubstantially integral parts thereof. Thus they are guides for thepiston-head that do not give at all as do spring-urged and similarelements that permit rocking and/or slapping of the piston under thestresses to which it is subjected.

The auxiliary skirts and replaceable packingrings, as renewable elementsof a piston structure, may prolong indefinitely the life of the integralparts of the structure.

If desired, the auxiliary skirts may be strengthened by a lower marginalrib 35.

What I claim as new, and desire to secure by Letters Patent, is

1. A piston comprising a head, an integral skirt of less diameter thanand connected directly to said head and extending to the other end ofthe piston structure and flattened exteriorly at opposite places, andrigidly and non-yieldingly secured to each side of said skirt aremovable auxiliary skirt of substantially the same exterior diameter assaid head, said two auxiliary skirts interiorly conforming in contour tothe flattened and arcuate surfaces of said integral skirt, and saidsurfaces abutting substantially the entire area of said auxiliary skirt.

2. A piston comprising a head, an integral skirt of less diameter thanand connected directly to said head extending to the other end of thepiston structure and flattened exteriorly at opposite places, andrigidly and non-yieldingly secured to each side of said skirt aremovable auxiliary skirt of substantially the same exterior diameter assaid head, each of said auxiliary skirts having in its median portion athickened part presenting a flat inner surface conforming to and seatedagainst a fiat of said integral skirt, said two auxiliary skirtsinteriorly conforming in their arcuate portions to the arcuate surfacesof said integral skirt, and said latter surfaces abutting substantiallythe entire arcuate area of said auxiliary skirts.

- EMIL NELSON.

